The present invention relates generally to a lamp string comprising a number of lamps connected by electrical wires, and in particular to a size-reduced, watertight lamp structure of the lamp string.
Lamp strings are widely used in celebration of holidays and festivals. A lamp string comprises a number of lamps connected by electrical wires. Each lamp comprises a socket attached to the wires and a bulb received in the socket for electrical engagement with the wires. A major concern in the manufacturing of the light string is the reduction of material used. A feasible way is to reduce the dimension of the socket in the direction of bulb insertion. U.S. Pat. No. 6,376,974 discloses a shortened socket for reducing material used. Cutoffs are formed in the socket for further reducing the amount of material used.
Such a conventional socket, although effective in reducing the material used, is not watertight. Since the lamp strings are commonly used outdoors, watertightness is a concern of operation safety of the lamp strings. U.S. Pat. No. 5,791,940 teaches a watertight socket for lamp strings. The conventional watertight socket, however, is difficult to manufacture and has a complicated structure that increases costs and the amount of material used. In addition, part tolerance must be precise in order to achieve watertightness. Further, parts of the socket can be easily separated thereby lacking of operation safety
An object of the present invention is to provide a lamp string comprising a number of lamps that have a compact structure and thus low costs.
Another object of the present invention is to provide a lamp string comprising a number of lamps of which parts are securely fixed together for operation safety.
A further object of the present invention is to provide a lamp string comprising a number of lamps that have a compact and watertight structure for operation safety and cost reduction.
Yet a further object of the present invention is to provide a lamp structure of a lamp string that is suitable for both two-wire lamp and three-wire lamp.
A further object of the present invention is to provide a lamp structure of a lamp string wherein the lamp comprises a socket defining two isolated chambers respectively accommodating terminals of the lamp for eliminating potential risk of electric shorting.
To achieve the above objects, in accordance with the present invention, there is provided a lamp swing comprising a number of lamps connected by wires. Each lamp comprises a bulb having conductive terminals and a retainer comprising a cylinder having a top opening for receiving the bulb and a U-shaped support having a bottom with two arms extended towards and connected to a lower side of the cylinder for supporting and retaining the bulb in the retainer whereby opposite openings are formed between the two arms of the support. Projections extend from opposite sides of the support and extend in opposite directions. A partition extends from the bottom of the support and having opposite side faces that are inclined and converge to each other. A socket comprises a circumferential wall forming an upper space for receiving the retainer therein and a lower space having a lower opening for extension of the wires. A securing structure is formed on an inside surface of the circumferential wall and corresponds to each of the openings between the support and the cylinder of the retainer. Each securing structure includes two spaced first ribs received in the opening and engaging corresponding arms of the support of the retainer and a second rib for engaging the projection of the retainer to secure the retainer in the socket. Channels are defined in the circumferential wall in the lower space for receivingly engaging the side faces of the partition of the retainer. A conductive pad is mounted to each wire and is located in a chamber formed between the securing structures and the circumferential wall of the socket for engaging the terminals of the bulb.